1bnc
THREE-DIMENSIONAL STRUCTURE OF THE BIOTIN CARBOXYLASE SUBUNIT OF ACETYL-COA CARBOXYLASE
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OverviewOverview
Acetyl-CoA carboxylase is found in all animals, plants, and bacteria and, catalyzes the first committed step in fatty acid synthesis. It is a, multicomponent enzyme containing a biotin carboxylase activity, a biotin, carboxyl carrier protein, and a carboxyltransferase functionality. Here we, report the X-ray structure of the biotin carboxylase component from, Escherichia coli determined to 2.4-A resolution. The structure was solved, by a combination of multiple isomorphous replacement and electron density, modification procedures. The overall fold of the molecule may be described, in terms of three structural domains. The N-terminal region, formed by Met, 1-Ile 103, adopts a dinucleotide binding motif with five strands of, parallel beta-sheet flanked on either side by alpha-helices. The, "B-domain" extends from the main body of the subunit where it folds into, two alpha-helical regions and three strands of beta-sheet. Following the, excursion into the B-domain, the polypeptide chain folds back into the, body of the protein where it forms an eight-stranded antiparallel, beta-sheet. In addition to this major secondary structural element, the, C-terminal domain also contains a smaller three-stranded antiparallel, beta-sheet and seven alpha-helices. The active site of the enzyme has been, identified tentatively by a difference Fourier map calculated between, X-ray data from the native crystals and from crystals soaked in a, Ag+/biotin complex. Those amino acid residues believed to form part of the, active site pocket include His 209-Glu 211, His 236-Glu 241, Glu 276, Ile, 287-Glu 296, and Arg 338.2+ represents the first X-ray model of a, biotin-dependent carboxylase.
About this StructureAbout this Structure
1BNC is a Single protein structure of sequence from Escherichia coli with PO4 as ligand. Active as Biotin carboxylase, with EC number 6.3.4.14 Full crystallographic information is available from OCA.
ReferenceReference
Three-dimensional structure of the biotin carboxylase subunit of acetyl-CoA carboxylase., Waldrop GL, Rayment I, Holden HM, Biochemistry. 1994 Aug 30;33(34):10249-56. PMID:7915138
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